Method for extruding porous irrigation pipe

ABSTRACT

A porous pipe primarily of rubber and synthetic rubber reclaimed from rubber tires, ground to a relatively small granular size, with metal removed; such as, for example, would pass through a 30-mesh screen, process-mixed through a pipe extruder, with a much smaller binder mix of primarily polyethylene, along with vinyl, ABS binder, and a trace of attaclay. The resulting product is useful as a subsurface irrigation buried pipe, having high structural integrity effectively resisting soil-loading pipe collapse, and it even resists collapse from moderately large rocks in the soil, and yet has a high degree of flexibility along its length. A pipe is provided with cross sectional area of pipe wall more than twice the cross sectional area of the pipe opening. It is a waterleaking pipe formed in the process through the extruder with limited foaming from steam originating from absorbed moisture in the ground, reclaimed rubber tire material, and from residual gasses venting from the material mix, with product mix heating in the extruder, forming some open cell fluid flow paths. The foaming with steam and gasses from the mix also form labyrinth passageways between the rubber tire granuals and the polyethylene binder mix, and also through the binder mix that is non-compatible with the rubber granules but that forms a physical interconnective structural material binder therefor.

This is a division of application Ser. No. 445,866, filed Feb. 26, 1974now U.S. Pat. No. 4,003,408.

This invention relates in general to the manufacture of irrigationsystems and, in particular, to an irrigation porous pipe processedprimarily of reclaimed material from rubber tires, ground to smallgranular size, mixed with a binder, mainly of polyethylene, with wallingsized to withstand soil loading in an underground irrigationenvironment.

For healthy plant growth and optimized crop production, and with turfgrasses, it is water in the root zone area of the soil that counts. Withabove-ground watering, the water must enter the soil and penetrate tothe root zone if it is to benefit the growing plants. Moisture that wetsonly the above-ground portions of grass plants and the layers of organicmaterial and soil above the root is of particularly no value, and may beharmful with mineral salt crustation build-up through evaporationdepositions of mineral content at the surface. A dense sod, for example,may absorb a quarter-inch or more of water before any of it enters thesoil. Light, above-ground waterings encourage shallow rooting, thusproducing plants that are subject to quickly drying out during intervalsof no watering. Water lost through evaporation and run-off, withabove-ground surface watering systems is a significant adverse factor inwater shortage areas where the ground water table is relatively deep,and water pumping is required, and where water must be supplied overgreat distances. Above-ground watering encounters timing problems inthat moist foliage overnight encourages plant diseases. Further, mostgolf courses are closed down at least one day a week, with above-groundwatering generally presently used, being in many instances high pressuresprinkling systems. Another consideration in the production of a newproduct is the availability of raw material in this day of shortages,and if it can be made primarily of reclaimed rubber, and/or syntheticrubber, from used tires that present a severe disposal problem, so muchthe better. Many sprinkling systems have continuing labor andmaintenance costs, with requirements such as moving sprinklers, walkingthe line, pop up or protruding sprinkler heads that many times arestruck and damaged or broken off by mowers or other equipment. Further,freeze-up of pipes and other water carrying equipment is a problem, andwith severe cold waves, many times causes costly damage. Anotherconsideration is that of interference with normal yard work, with, forexample, a porous pipe water distribution system with leaky pipe buriedat an underground depth of ten inches or more, allowing all normal yardwork, including roto-tilling. It is also important that nutrients andhealth-giving ingredients, some insecticides and, in some instances,herbicides, be distributed directly to the subsurface root zone in thesoil of areas being irrigated. Growth of weeds should be minimizedrather than enhanced, and cultivation requirements with cash cropsoptimally minimized.

Underground irrigation, to many, falls under the general category ofdrip irrigation used, in any event, in the daily maintenance of anadequate section of the root zones of plants with moisture somewherebetween dampness and saturation or field capacity throughout the growingseason. This system enables the attainment of an optimizedsoil-water-plant relationship that is conducive to much better growthand substantially better yields, with less water applied. Evaporation issubstantially totally eliminated, pipes are out of the way of people andmachinery, and water, along with fertilizer when used, is applied whereit obviously does the most good, right at the roots. Water seeps fromthe underground pipe, and by capillary action and absorption spreadsthrough the root system, maintaining a constant moisture levelthroughout the area of treatment.

Variation in the water level content in soil can create many problems,with, for example, expansion and contraction of soil under and aroundslab foundations. This can be such as to cause foundations to shiftaround and/or cracking of the foundations, brick walls, inside plaster,and sheetrock walls in homes. Thus, an underground system formaintaining a stabilized soil moisture state would go far in eliminatingsuch disasterous home and building damage. Aeration is important insewage treatment systems, with air pumped into and bubbled upwardthrough affluent in anaerobic action fluid treatment ponds and tanks,however, in most instances, attainment of desired bubble size is aproblem. Most pumped-in, formed air bubbles, in many installations, aretoo large and gravitate to the surface much too rapidly, so any systemthat would create small bubbles such as would very slowly drift upwardthrough an affluent mix, is highly desired.

It is therefore a principal object of this invention to provide a methodfor the manufacture of an underground irrigation system capable ofefficiently supplying water and fertilizers to the root zone of plants,without soil structure damage.

Another object with such an underground irrigation system is to minimizewater requirements, to minimize evaporation loss to the air, and toavoid mineral salt build-up in the soil.

A further object is to attain a steady, slow-weeping application ofwater, feeding a capilary absorption distribution action through soilthrough needed periods of water irrigation.

Still another object is the attainment of stabilized soil conditionsunder and around building foundations and other structures such asswimming pools.

Features of this invention useful in accomplishing the above objectsinclude, in an underground irrigation porous pipe, a pipe made primarilyof ground-up reclaimed rubber and/or synthetic rubber, such as obtainedfrom old tires. The reclaimed rubber granuals, that are ground to a sizesuch as would pass through a 30-mesh screen, are process-mixed through apipe extruder, with a much smaller amount of binder ingredients thattypically includes: a binder mix of primarily polyethylene, along withvinyl, ABS binder, and a trace of attaclay. The transversecross-sectional area of the pipe walls is substantial, in relation tothe cross-sectional area of the pipe opening, and is thick enough tohave labyrinth passageways for seeping of water to the exterior of thepipe without soil-damaging water jets. The pipe is a subsurfaceirrigation buried pipe having high structural integrity effectivelyresisting soil-loading pipe collapse, while also having a high degree offlexibility along its length. The pipe is formed in the process throughthe extruder, with limited foaming from steam originating from absorbedmoisture in the ground, reclaimed rubber tire material, and fromresidual gasses venting from the material mix, with product mix heatingin the extruder, forming some open-cell fluid flow paths. Labyrinthpassageways between rubber tire granular material and polyethylenebinder mix, and through the binder mix, are also formed with the steamand gas foaming, or blowing, as the pipe is extrusion process formed.

A specific embodiment representing what is presently regarded as thebest mode of carrying out the invention is illustrated in theaccompanying drawings.

In the drawings:

FIG. 1 represents a partial side elevation view of applicant'sunderground irrigation porous pipe;

FIG. 2, an end view of the pipe of FIG. 1;

FIG. 3A, an enlarged section of pipe walls taken along line 3 -- 3 ofFIG. 2;

FIG. 3B, a further enlargement of a small portion of the pipe wallsection of FIG. 3A;

FIG. 4A, a partially cut away and sectioned view of a vented andtemperature regulated screw type extruder used in producing the porouspipe;

FIG. 4B, a partial side elevation view of a long, extended, cold watertank (or trough) receiving hot pipe from the extruder die, a pipepuller, and a pipe coiler;

FIG. 5, a partially cut away and sectioned view of the extruder die tipend; and,

FIG. 6, a gallons-per-hour per 100ft. flow rate to pressure graph for a300 ft. long section of 1/2 in. I.D. leaky pipe.

Referring to the drawings:

The porous pipe 10 with a short length, shown in FIG. 1, and in end viewin FIG. 2, is made primarily of reclaimed rubber-like, previouslyvulcanized material such as that recovered from chopped-up old rubbertires with the metal removed. This rubber-like, previously vulcanizedmaterial is reground to generally less than one-sixteenth inch diametergranual size, even down to a size that passes through a 30-mesh screen,before being process mixed with binder material, forming a matrixinterlocking the rubber-like granuals in the processed pipe 10. Whilethe wall 11 thickness to pipe I.D. is such, with the pipe materialcompounded for the finished pipe, to give good structural integrityagainst soil loading collapse when buried in the soil as an undergroundirrigation water seeping pipe, it has a high degree of flexibility alongits length in adjusting to required bends and turns necessary forunderground installations. Foaming or blowing during product mixprocessing to the finished pipe 10 forms random pockets 12 (or voids) inthe pipe wall 11, such as shown in more detail in the wall sectionenlargement of FIG. 3A where passageways to the exterior are not formed,or are late in forming with the blowing process action. Irregularlyshaped labyrinth type channels 13 (shown in the further enlargement ofFIG. 3B, an enlargement in the order of approximately 120X), formed inthe blowing process action are an essential feature of the finishedporous pipe product. Enough blow process formed channels 13 are formed,interconnecting the inner surface 14 and outer surface 15 of the pipe10, either individually or via interconnected channels 13, to providethe desired through-the-wall seepage passageways. While the blowingformed pockets 12 are not the desired result, some of them dointerconnect with some blowing process formed channels 13, as part ofsome of the through-the-wall seepage passageways. The desired blowingprocess is provided primarily with steam from moisture previouslyabsorbed by the previously vulcanized material granuals 16, and someresidual gases in the granuals and/or binder material used in makingpipe 10, with most blowing process formed labyrinth type channels 13being developed in and through the interconnecting matrices 17 formed bythe binder material interlocking the granuals 16 into the product pipe10. With processing of the pipe, while the granuals 16 generally retaintheir physical integrity, there is some degree of surface materialwelding or merging with the binder material.

Porous pipe 10 is extruded from a two stage wave screw extruder 18, suchas shown in FIG. 4A, with the ingredient mix fed from hopper 19 to theproduct mix drive wave screw 20 contained within and extending throughsubstantially the entire length of the relatively long extruder cylinder21. Extruder 18 is generally typical of screw type extruderscommercially available in both this country and abroad, equipped with adrive motor 22, a gear drive train section 23 output driving the wavescrew 20. The extruder 18 is also equipped with a plurality of heatingand cooling cylinder barrels 24 longitudinally positioned along thelength of extruder cylinder 21, with each having cast-in resistanceelements connected through wires 25 and 26, and cast-in cooling coilsconnected through cooling fluid lines 27 and 28 to electrical powersource control 29 and cooling fluid source control 30, such as shownwith only one of the cylinder barrels 24, as a matter of convenience. Avent 31, connected to a vacuum control 32, is positioned at anyconvenient location along the extruder cylinder 21 and wave screw 20,longitudinally, after the product mix temperature has risen, throughheating control and product mix working, that blow venting can occurthrough the binder material content of the product mix. The other vent31 position constraint is that it must be positioned far enough ahead ofpressure head screen 33 that there is not as yet a reflected backpressure build up at that location along the wave screw 20. The productmix, forced through pressure head screen 33, is extruded from theextruder die 34 where effective blowing creation of irregularly shapedlabyrinth type channels 13 occurs with lowering of product materialpressure from the high pressures at pressure head screen 33 down toatmospheric pressure. The feed throat member 35 below hopper 19 may beequipped with cooling and/or heating structure to further aid intemperature control of the product mix and extension of the possiblepositioning range of vent 31 toward the hopper 19.

Porous pipe 10 being extruded from the extruder die 34 very quicklyenters, as shown in FIG. 4B, a cooling trough 36, approximately 40 feetlong, filled with chilled water, at approximately 35° F. This quicklycongeals the pipe binder matrices, with the blowing generated throughwall passageways desired in the finished product. The pipe 10 is drawnfrom the cooling trough 36 by rubber tired, wheeled 37 and 38 pullerassembly 39, and passed to a conventional reel pipe coiler 40.

Referring also to the enlarged extruder die 34 tip end of the extruder18 product mix forced through pressure head screen 33 flows by thinvains 41 extended from mount ring 42 as supports for porous pipe I.D.die mandrel 43 and mandrel base 44 into which the I.D. die mandrel 43 isthreaded. A center opening 45 in I.D. mandrel 43 is connected throughpassage 46 in base 44 and pipe 46 to the exterior for venting of theinterior of pipe being die extruded to atmosphere as it first comes fromthe die.

Excellent product production runs are obtained, for example, withprevulcanized material granuals ground from old rubber tires with metalremoved but soft cording remnants remaining in a granular sizeconsistency that would pass through a 30 mesh screen. Theseprevulcanized material granuals, as approximately 70% of the productmix, are mixed with the remaining 30% of the product mix in the hopper19 of extruder 18. This is with the 30% of the product mix comprised of,by percentages:

Polyethylene (high density) -- 70%

Vinyl -- 14%

ABS (Binder) -- 15% Attaclay -- 1%

The product mix is fed from the hopper 19 into the input end of theextruder cylinder 21 to product mix drive screw 20, where heat input andheat of working initially brings the product mix temperature up toapproximately 300° F. Next, down the screw drive in the direction ofmaterial flow, before, and as the product mix approaches vent 31, theproduct mix temperaure is raised to approximately 350° F, generally inthe range of 350° to 400° F, and then with venting and immediatelythereafter the product mix is cooled down to approximately 300° F. Thenthe product mix is heated up again to approximately 350° F as theproduct mix is approaching the pressure head screen 33, along with apressure build up to the approximate range of 2000 to 3500 p.s.i. at thescrew 20 drive pressure side of the pressure head screen 33. The processtemperatures used are generally high enough to transform the bindermaterial content of the product mix to the moulten fluid plastic statesuch that flow venting can occur there through while the pre-vulcanizedmaterial granular generally retain their integrity, other than for somedegree of surface welding or merging with the binder material in theinterconnecting matrices 17. The porous pipe 10 is screw pushed outthrough the extruder die 34 into cooling trough 36 from which it ispulled and then rolled. Venting to a vacuum of 20 inches of mercury atvent 31 gives a product standard pipe with a seepage flow rate of 15gallons per 100 feet per hour at five p.s.i. internal water pressure, asshown in FIG. 6, with the effective blow venting seepage passage actionoccurring as the pipe 10 is being extruded to the atmosphere. Venting toa five inch mercury vacuum with approximately the same product processtemperatures results in the highest leak pipe rate of 40 gallons per 100feet per hour at 5 pounds p.s.i. water pressure. Further, venting to 25inches of mercury vacuum results in the lowest leak pipe, with 12gallons per 100 feet per hour at 5 pounds p.s.i. water pressure. Theventing provided at vent 31 is quite effective at the product mixtemperature at that process location at stabilizing the residualmoisture and gas content in the product mix for good uniform blowingaction control as pipe 10 is extruded to atmosphere from the die end 34.

The product mix may be varied with the pre-vulcanized material granualsbeing in the range of approximately 60 to 90 per cent of the productmix, and the binder material being in the corresponding related range ofapproximately 40 to 10 per cent of the product mix. Further, the bindermaterial may be the mix previously outlined, or any one or two of thematerials including polyethylene, vinyl, ABS (binder) with a trace ofattaclay, or without, as may be used for product variation results asdesired. In any event, the binder substance (whether of one or moreingredients) is transformed to the plastic or moulten state at theprocess temperatures used, and with mixing action within the screwextruder while the previously vulcanized material granuals generallyretain their structural integrity.

Whereas this invention is herein illustrated and described primarilywith respect to several embodiments hereof, it should be realized thatvarious changes may be made without departing from essentialcontributions to the art made by the teachings hereof.

I claim:
 1. A method of extruding porous irrigation pipe and the likecomprising:forming a mixture of granular elastomeric material havingresidual moisture therein and a plasticizable binder material, feedingthe mixture into and through an extruder to plasticize said bindermaterial, extruding said pipe from said extruder with said residualmoisture being vaporized and with said binder material interlocking thegranules of said elastomeric material to form labyrinth-typechannel-like apertures in said pipe as said mixture is extruded, andmaintaining said elastomeric material in granular form during theextrusion of said pipe.
 2. The method described in claim 1 wherein saidelastomeric material is vulcanized granular material of generally lessthan one-sixteenth inch diameter.
 3. The method described in claim 2wherein said binder includes polyethylene.